In completing wells in poorly consolidated or unconsolidated formations, consideration must be given to sand problems likely to arise during the operation of the well. The incompetent nature of this type of formation requires that a well completion technique include means for excluding sand production. Erosion and plugging effects of sand entrained in produced fluids are well known and if not arrested can seriously reduce well productivity.
The propensity of a formation to produce sand is particularly acute in formations characterized as unconsolidated or poorly consolidated. These terms, as applied to subterranean sedimentary deposits, define a particular class of sedimentary rock, the distinguishing characteristic of which is the absence of a rock matrix made up of sand grains bound into a cohesive mass.
A widely used sand control technique is the gravel pack installation which operates on the principle of forming a sand exclusion zone in surrounding relation to the wellbore. The sand exclusion zone composed of particularly graded aggregate screens out or bridges the formation sand entrained in the produced fluids. The typical gravel pack completion involves the placement of aggregate in the immediate vicinity of the wellbore and the provision of a support means for maintaining the aggregate in place. The aggregate is generally a specially graded sand or gravel, but can be other particulate material such as walnut shells, glass beads, and the like.
The placement of the aggregate immediately adjacent to the producing formation presents a major source of trouble in performing the gravel pack installation. Packing gravel into perforations is usually achieved by squeeze packing. Squeeze gravel packing is a two-stage process which includes (1) transportation of gravel slurry down through the pipe; and (2) gravel pack buildup at the formation face as fluid leaks off through the formation. In gravel packing of heterogeneous pays, frequently those perforations penetrating a lower permeability formation are at best partially packed. Additionally, even when properly packed, fluids are not produced through some perforations because formation fines accumulate in channels of the formation prior to gravel packing them. Accumulation of fines within these channels prevents hydrocarbonaceous fluids from flowing out of the reservoir into the wellbore for production to the surface.
Therefore, what is needed is a method to prevent fines from accumulating and plugging perforation channels after gravel packing a wellbore so as to increase the production of hydrocarbonaceous fluids from a reservoir.